You forget that each subcontractor writes the specs for its modules. So Subcontractor X specs theirs as being grossly overweight and overpower. The system integrator bitches them out but budgets for overages. After a reasonable amount of time has elapsed, Subcontractir X reveals a miracle: their wonder engineering team has got the module nearly down to the target budget. Attaboys are dispensed to the worker bees, champagne to the management, and the spy module gets installed.